PORTLAND - If you thought the great dam building era of the Northwest was long over, you might be mistaken. But we're not talking about damming rivers here. This is about building long earthen dams to make new off-stream hydropower reservoirs. They're being designed to act as giant batteries and shock absorbers for the electric grid.

Here's an odd thought that relates to keeping your lights burning steady and bright. Someday a small portion of your electricity bill could go toward pumping water in a loop. Lots of water. Pumped uphill, run back downhill, then pumped back uphill again.

Enterprising energy developers have at least seven places in the Northwest in mind for projects of this type.

Erik Steimle is shepherding a proposal for two reservoirs near Klamath Falls, one up on a plateau connected to another down below in the valley.

"It's a large reclamation project, yes," Steimle says. "Hundreds of workers on site. The construction project would likely take place over the course of years ... a large project."

Steimle works in the Portland regional office of energy developer Riverbank Power. On the walls are renderings of what in the biz they call a pumped storage hydropower project. Steimle gets help explaining how it works from Ellis Arzu of joint venture partner enXco.

"On energy generation, what we're talking about is a simple arbitrage between pumping using low cost energy, so basically off peak, and generating the energy at peak hours of the day," Arzu explains.

In other words, the good old Wall Street principle of buy low, sell high. But Arzu says that alone doesn't net much money given this region's generally low electricity prices. So the developers are marketing their project as a grid stability service.

They propose to make most of their money billing utilities for backing up -- or "balancing" -- the volatile, irregular output of the Northwest's burgeoning fleet of wind farms.

"So the wind stops blowing. There's no energy from that wind farm. What happens at that point?" Arzu asks.

Call me, he says in so many words. Conversely, Arzu says his project could soak up excess power when wind and solar farms overproduce and hydroelectric dams are maxing out with spring runoff.

Pumping water uphill consumes lots of electricity. The upper reservoir then essentially acts like a big battery. It can later release the water on demand to run downhill through a generator. That effectively time shifts the irregular power production.

Multiple energy developers are proposing this sort of hydropower project in the Northwest. The Klickitat Public Utility District has applied for a federal permit to build two connected reservoirs at the east end of the Columbia Gorge.

"As soon as wind development started going -- let me put it -- crazy in the area, we kind of recognized probably it was time to start working on a project like this," says PUD's general manager Jim Smith.

There are other competing proposals in eastern Washington near Grand Coulee, also in eastern Oregon and southern Idaho. Whichever end up happening, the construction price tags are staggering -- in the neighborhood of $2 billion.

"That is the challenge, who pays for this?" asks Rick Miller, a nationally-known hydropower consultant with HDR Engineering. "Since it is a regional grid benefit, there are a lot of discussions going on that maybe everybody pays a very small portion of their power bill that would go to contribute to this type of an asset."

Major Northwest utilities haven't yet been convinced they should pay a third-party to ensure grid stability. That's one reason why the big reservoir projects we're talking about could take five to 10 years to develop.

Area utilities are also looking at cheaper alternatives, which include your basic natural gas backup power plant and a variety of more exotic options. All of these have their own limitations though.